The conventional LED lamp tubes adopted for outdoor illumination and used in high humidity environments mostly have an LED lamp strip sealed in a plastic tube via sealant to achieve waterproof effect. But such a structure does not provide desirable heat dissipation for the lamp tube. To remedy this problem another design has been adopted by fabricating a heat conductive aluminum casing to seal the LED lamp strip inside via resin. However, such a design requires complicated process, and the product also is not repairable. In other occasions, such as illumination in a cryogenic environment like providing lighting for the interior of refrigerators, uniform illumination is required. Although the conventional fluorescent lamp can provide a wide projection angle, illumination attenuates drastically. As a result, luminosity is deficient in the middle portion of the refrigerator or luminosity is greater at two sides. This results in less desirable overall illumination uniformity. How to design the LED lamp with a specific projection angle to achieve greater luminosity and total uniformity is an urgent issue remained to be resolved in the industry. Moreover, the conventional LED lamp tubes generally have power lines threading through from one side. Such a structure makes installation more difficult and also creates a great deal of confusion during installation with prolific types of LED lamps. To reduce the problems of numerous LED lamp types and complex installation, a common model of the LED lamp is adopted to meet a wide variety of requirements.